A wireless local area network (WLAN) may include a basic service set (BSS). The BSS may include an access point (AP) and one or more stations (STA). The AP may transmit data frames to the one or more stations over a downlink channel and may receive data frames over an uplink channel. In a high throughput WLAN the uplink and the downlink channels may employ an intensive traffic of data frames. The BSS may include a Direct Link Service (DLS) to allow the stations to transfer data between the stations without the AP intervention. The sequence of frames that may be used to transmit data from one station to one or more other stations, and to receive a response(s) from the one or more stations, may be referred to as a transmit sequence. The transmit sequence may include an aggregation of data units which may be transmitted by an Initiator, and one or more response frames from a Responder. For example, the Initiator may be an AP and the Responder may be a mobile unit.
In WLAN a collision of transmissions from different mobile units and the AP may occur. In order to avoid collisions the AP may initiate a transmit opportunity (TxOP) time slot. In the TxOP time slot the AP, for example, an Initiator, may transmit data frames to a mobile station (e.g. a Responder). For example, according to IEEE 802.11e standard, only an owner of the TxOP may be allowed to transmit during the TxOP time slot. Thus, TxOP time slot may not be fully occupied by transmissions of the Initiator and the Responder.
It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.